1. Field of the Invention
This invention relates to a stretch blow bottle made from a polyester resin composition and production thereof. More particularly, The invention relates to a stretch blow bottle made from a polyester resin composition comprising a polyethylene terephthalate resin and a polyethylene isophthalate resin, and a process for producing the same.
2. Description of the Prior Art
Plastics bottles which are not deformed when filled with beverages, but remain self-supported are widely used as containers for various kinds of beverages, such as carbonated beverages, carbonated beverages containing fruit juice, soft drinks, mineral water and tea. While various kinds of plastics have been used for making such bottles, stretch blow bottles made from a polyethylene terephthalate resin are, among others, widely used owing to their high levels of transparency, gas-barrier property, heat resistance and mechanical strength.
The bottled beverages leaving a bottling plant are distributed through many routes before they are sold by retail stores to consumers. The known stretch blow bottles made from a polyethylene terephthalate resin are, however, not satisfactory in gas-barrier property, but if the bottled beverages are left to stand for a considerably long time, it is likely that the release of carbon dioxide from the beverages may result in the failure to maintain an initial gas pressure, or that oxygen may enter the bottles and deteriorate their contents.
Japanese Patent Publications Nos. 1-49384 and 5-13987, for example, propose the blending of a polyethylene terephthalate resin with a polyethylene isophthalate resin to improve the gas-barrier property of the former. Such a blend has shown an improved gas-barrier property and a high transparency. However, it has been likely that, if a bottle produced therefrom is dropped on the ground, or on a concrete floor, it may have its bottom separated in a layer at the portion at which the bottle hits against the floor, as if abraded, and allow its contents to leak out. Similarly, a layer of separation has also been found in a section exposed by cutting the body of such a bottle with a knife.
The present inventors have molded a preform from a resin composition comprising a polyethylene terephthalate resin and a polyethylene isophthalate resin and studied the microscopic dispersion of the polyethylene isophthalate resin in the polyethylene terephthalate resin as the matrix in the preform prior to its stretch blow molding in order to find a solution to the problems as pointed out above with respect to the conventional stretch blow bottle made of a polyester resin composition. As results, they have found that if the microscopic dispersion of the polyethylene isophthalate resin in the matrix of the polyethylene terephthalate resin fulfils the specific conditions, the resultant resin composition exhibits a high gas-barrier property and gives by stretch blow molding a self-supported bottle of high mechanical strength not having the bottom separated in a layer, even if it may be dropped on the ground, or a concrete floor.
It is, therefore, an object of this invention to provide a self-supported stretch blow bottle for a beverage made from a polyester resin composition, and having a high gas-barrier property and a high mechanical strength including breaking and impact strength.
It is another object of the invention to provide a process for producing such a polyester stretch blow bottle.
The invention provides a stretch blow bottle made from a polyester resin composition which comprises: (A) 60 to 99% by weight of a polyethylene terephthalate resin and (B) 1 to 40% by weight of a polyethylene isophthalate resin, wherein 300 square microns of a section exposed by cutting the neck of the bottle contains less than one particle of the polyethylene isophthalate resin (B) having a diameter of 0.1 micron or above in the polyethylene terephthalate resin (A) as the matrix.
The invention further provides a process for producing a polyester stretch blow bottle which comprises:
melt kneading under a high shear load a resin composition comprising (A) 60 to 99% by weight of a polyethylene terephthalate resin and (B) 1 to 40% by weight of a polyethylene isophthalate resin;
forming a preform from it at a temperature of 250xc2x0 C. to 310xc2x0 C.; and
stretch blow molding the preform;
wherein 300 square microns of a section exposed by cutting any portion of the preform contains less than one particle of the polyethylene isophthalate resin (B) having a diameter of 0.1 micron or above in the polyethylene terephthalate resin (A) as the matrix.
The bottle of the invention has a high gas-barrier property owing to the microscopic dispersion of the polyethylene isophthalate resin as defined hereinabove in the matrix of the polyethylene terephthalate resin. It also exhibits a high level of transparency and a high level of mechanical strength. In addition, even if it is dropped on the ground, or on a concrete floor, it does not have the bottom separated in a layer at which it hits against the ground or floor. For example, no bottle of the invention having a capacity of 100 ml or above, and filled substantially with water has a cracked bottom, even if it may be dropped five times on a concrete floor from a height of 2 m with its bottom down.
Thus, the bottle of the invention is suitable for use in containing, among others, a carbonated beverage, or any other beverage that is liable to deterioration, such as a fruit juice, or vitamin drink. The used bottles can easily be melted, and reused in making bottles, or other molded products.
Other features and advantages of the invention will become apparent from the following description and the accompanying drawing.